EXPLANATION OF PLATES. 



All of figures on Plates XXXIV-XXXIX, with the exception of the photo-micro- 

 graphs, are photographs of plants floating in water, in aquaria, or in specimen jars. 



Plate XXII. 



Poiamogeton americanus, seed, ij/^ times natiiral size. 

 Poiamogeton americanus, seedling 5 days old, i>2 times natural size. 

 Poiamogeton americanus, seedling 14 days old, i^^ times natural size. 

 Poiamogeton americanus , seedling of four months, ^2 natural size; A, winter buds. 

 Poiamogeton americanus. germinating winter bud, natural size; the last two winter buds 

 belated in development. Aquarium specimen, January 24, 1914. 



Fig. 6. Poiamogeton americanus, rootstock with winter bud A. natural size. September. 



Plate XXIII. 



Fig. 7. Poiamogeton amplif alius , rootstock, }4 natural size; A, A, A, young shoots which continue 

 to grow slowly through winter. November. 



Fig. 8. Poiamogeton heierophyllus, submerged plant, ^^ nattu-al size; A, tuberous rootstock; B, B, 

 submerged shoots; a, b, and c, details of leaves. May 4. 



Fig. 9. Poiamogeton heterophyllus, rootstock not tuberous, natural size. July 7. 



Fig. 10. Po/a»no<;t';o)j /!eicro/>/!)'//Hs-, tuberous rootstock, natural size. July 7. 



Fig. II. Poiamogeton heierophyllus, tuberous rootstock, natural size; A, A, incipient shoots 

 November 17. 



Plate XXIV. 



Fig. 12. Poiamogeton heterophyllus, typical habit of land form, 13-2 times natural size. Terminal 

 portion of rootstock tuberous. July 7. 



Fig. 13. Poiamogeton heierophyllus, terminal portion of rootstock showing tendency to become 

 tuberous, 1J-2 times natural size. July 7. 



Fig. 14. Same, more advanced stage, 1% times nattiral size. July 7. 



Fig. 15. Po/amoyeZoii Aeiero^Aj//M.f, aquarium specimen, natural size; A, tuberous internode placed 

 in aquarium in November; B, B, new shoots and rootstock. Januarj' 26. 



Plate XXV. 



Fig. 16. Poiamogeton heterophyllus, aquarium specimen, natural size; A, B, C. D, new shoot and 

 tuberous rootstocks in various stages of growth. March 14. 



Fig. 17. Poiamogeton heierophyllus, aquarium specimen, natural size. 



Fig. 18. Poiamogeton perfoliatus, winter shoot showing elongation of intemodes, natural size; A, 

 leathery scale ; a, detail of scale. June. 



Fig. 19. Growing tips of same. 



Plate XXVI. 



Fig. 20. Poiamogeton crispus, recumbent branch, show'ing development 01 r.ew shoots on old stem, 

 ■/^ natural size. March. 



Fig. 21. Po/amope/on cm/)jYj, spicular bur, ij^ times natural size. Aquarium. July. 



Fig. 22. Poiamogeton crispus, denticulate bur, f^ natural size ; a, detail of leaf with denticulate 

 base, 2 times natural size; i, line delimiting starch storage. 



Fig. 23. Poiamogeton crispus, s\>TouXm%hvir, ij 2 times natural size. March. 



Fig. 24. Poiamogeton crispus, denticulate bur with sprout, natural size. Aquarium. July. 



Fig. 25. Po/a?HO(;rtoK cm/>M.y, spicular bur with sprout, ^ natural size. Aquarium. July. 



